Large blocks of carbon are employed as anode electrodes in the smelting process in which aluminum is manufactured. While an electrode is substantially consumed during its useful life, there does remain a fairly large volume of carbon left, particularly in the upper region of an electrode where metallic, electrical connecting rods are embedded in the carbon. Since the quantity of carbon left is fairly substantial, it is customary in the industry to reclaim it and use it in the manufacture of new carbon electrodes. Unfortunately, before this can be done, used electrodes must be cleaned to remove a surface encrustation of alumina and cryolite which builds up during the smelting process. This encrustation is white in color and thus easily distinguishable from carbon which is, of course, black. In general, three methods or approaches are known to be presently employed to remove this coating. In one, there is utilized a combination of manual hammering and scraping of the electrodes. In a second one, powered (pneumatically or hydraulically) scraping arms operate on the electrodes. In the third one, a vibrating scraping tool is employed. Significantly, each of the methods are generally regarded as being unduly slow and labor intensive.
Another pertinent factor is that smelting plants normally manufacture their own electrodes as a companion function to smelting, and thus the electrode manufacturing process must keep step with the smelting process. This requires that the labor force employed in cleaning electrodes always be maintained at or above a critical number or else some shutdown of the smelting operations may be necessary should the cleaning operation fall behind. Inasmuch as the time required to clean an electrode may vary significantly when performed as described, it is typical that a plant will err on the safe side and at times may have larger that necessary crews working in the cleaning operation. In any event, there is general agreement in the smelting industry that the electrode cleaning operation takes too much time and is too expensive.
Accordingly, it is an object of this invention to provide an improved system for the cleaning of large carbon electrodes.